1. Field of the Invention
The present invention relates to a variable flow mixing valve especially suited for use as a water faucet wherein either of two fluids may be delivered independently, or the two fluids may be mixed in preselected proportions for delivery.
2. Description of the Prior Art
Various forms of so-called mixing valves or faucets incorporating mixing valves have been developed for residential and other uses to deliver either of two fluids independently or to mix two fluids for delivery. Valves of this type are ordinarily used to deliver water at cold or hot supply temperatures, or at one or more intermediate temperatures, and at flow rates chosen by the user.
Early mixing valves consisted essentially of cold and hot water valve structures actuated by independent controls, but discharging jointly through a common spout. These dual control valves do not perform an internal mixing function but rather simply discharge regulated flows of cold and hot water through a common spout. A certain amount of skill is required by the user to independently adjust the dual flow controls to deliver water at a desired flow rate and at a desired temperature. If the controls are actuated to change the flow rate, the temperature of the mixed flow changes. Delivering water at a constant intermediate temperature throughout a range of available flow rates has been virtually impossible utilizing these early dual control valves.
More recently, mixing valves employing a single control have been developed. These single control valves typically provide a manually operable lever which is movable in one direction to deliver water at a selected temperature, and in another direction to provide a desired flow rate. Just as dual control valves require a certain amount of operator skill to effect delivery of water at a desired temperature and flow rate, single control valves likewise require a certain amount of operator skill to effect the desired operation. Trial and error positioning of the control is often required to obtain a mixed flow of desired temperature. To obtain a desired temperature at a desired flow rate is practically impossible and, if reached, is not repeatable.
The First Mixing Valve Patent presents a further advance in mixing valve art. Separate finger-operated controls are provided for supplying unmixed flows of cold and hot water. Additionally, one or more finger-operated controls are provided for supplying one or more mixed flows at a preselected intermediate temperature or temperatures. By this arrangement, each of the finger-operated controls regulates the delivery of water at a different delivery temperature. Delivery flow rate is established by positioning tbe proper control along its path of movement. Selection of the intermediate temperature or temperatures is effected by setting one or more flow restriction controls to properly proportion the relative rates of flow of cold and hot water which are supplied to each mixing chamber.
A primary valve element controls the admission of separate flows of cold and hot water to a mixing chamber. A secondary valve element regulates the flow of mixed fluid from the mixing chamber. The secondary valve element never closes completely and functions in concert with the primary valve element to assure the presence of a properly stabilized flow through the mixing chamber.
While the arrangement described in the First Mixing Valve Patent provides a rather easily serviceable unit which is producible as a durable structure at comparatively low cost, it does not provide a low cost operational "cartridge" which can be disposed of and readily replaced in the event the valve requires service. The First Mixing Valve Patent provided a very limited range of temperature adjustment and no control of maximum flow rate, and therefore was not acceptable. A problem not addressed by the First Mixing Valve Patent is the deterioration of the secondary elastomeric valve element due to repeated flexures and use of hot water, thereby losing complete control of temperature throughout the flow range. Moreover, some of the parts of the First Mixing Valve Patent require more complex fabrication techniques than are desirable, thereby adversely affecting the marketability of the device.
The Second Mixing Valve Patent discloses a multiple control mixing valve having a housing which is formed inexpensively as a stacked array of layer elements. The layer elements cooperate to define several overlying valve stages. A first stage is provided wherein (1) a flow of cold water is divided into at least two flow paths, (2) a flow of hot water is similarly divided into at least two flow paths, and (3) an adjustable restriction element is provided for controlling the flow rate along at least one of the cold and/or hot water flow paths.
Unrestricted flows of cold and hot water are delivered from the first stage to a second stage where separate lever-operated valve elements selectively control the admission of separate cold and hot flows directly to an outlet chamber located in a fourth stage. Proportioned flows of cold and hot water are delivered from the first stage to the second stage where one or more primary valve elements control the admission of these flows to one or more third stage mixing chambers. A separate secondary valve element controls discharge of mixed fluid from each of the third stage mixing chambers to the fourth stage outlet chamber.
A feature of the Second Mixing Valve Patent is a lost-motion or time delay mechanism operably interconnecting each set of primary and secondary valve elements to assure that a brief time interval lapses after the primary valve element opens before mixed fluid is permitted to discharge from the associated mixing chamber. Each of the lost-motion or time delay systems is designed such that some back pressure is maintained in its associated mixing chamber to attempt to maintain a constant temperature delivery throughout the available range of flow rates.
Although the Second Mixing Valve Patent has a variety of advantages as set forth in the patent, certain problems remain. The Second Mixing Valve Patent employs an elastomeric boot which overlies the outlet chamber and which is engaged by a plunger element to exert force through the boot to control the positioning of primary and secondary valve elements. It has been discovered that exposure to long term use and/or very hot fluids changes the characteristics of the seal such that the valve "chatters." The tendency of the valve to chatter generally renders it commercially unacceptable or, at least, suitable for use only in limited environments. Further, the deterioration of the secondary elastomeric valve element due to exposure to hot water and repeated flexures results in the inability of the valve to deliver water at constant temperature throughout the range of available flow rates. Compared to the First Mixing Valve Patent, the Second Mixing Valve Patent provides a somewhat increased temperature adjustment, but still has no control of maximum flow rate.